International Journal of Trend in Scientific
Research and Development (IJTSRD)
UGC Approved International Open Access Journal
ISSN No: 2456 - 6470 | www.ijtsrd.com | Volume - 1 | Issue – 5
Significance of Amphiphilic Block Copolymer Micelles and its
Characteristics
Tejas Joshi
Department of Chemistry,
UGC NON-SAP & DST-FIST Sponsored Department,
Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar, India
ABSTRACT
Amphiphilic block copolymers (ABCs) have been
used broadly in pharmaceutical applications. One of
the most widely used drug delivery systems is the self
assembly of ABCs carriers in micelle forms in
aqueous environment. Block copolymers have low
toxicity and due to their nontoxic properties and
surface-activity they have found application in the
areas of biomaterials, protein separation, drug
delivery and cardiovascular therapeutics and as
industrially important surfactants. ABCs micelles
have been the focus of research for the last many
decades. Research in the field has been increasingly
focused on achieving enhanced stability of the
micellar assembly, prolonged circulation times and
controlled release of the drug for optimal targeting.
Keywords: Block copolymer, amphiphilic, micelles,
surfactants
I.
INTRODUCTION
Simple polymer can be formed by joining monomer
units and become long chain polymer which is
revealed by Figure 1. Here monomer molecules united
to become long chain which is known as polymer.
Figure 1 Formation of polymer
Block copolymer is a linear arrangement where two
often-incompatible blocks obtained from different
monomers are covalently linked together. This basic
structure architecture in block copolymers provided
two distinct moieties behaving differently in solution
and thus these polymers possess structural resembles
to surface-active agents. Figure 2 is generalized
structure of block copolymer.
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International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470
Figure 2 Structure of block copolymer
There are various possibilities to form different
structure of block copolymers. In this way diblock (AB), triblock (A-B-A and B-A-B) and multiblock (or
segmented) polymers are possible. Amphiphilic drugs
bear an ionic or nonionic polar headgroup and a
hydrophobic portion. They tend to self-associate as
micelles in aqueous solution in a surfactant like
manner. Block copolymers possess unique structural
features resembling to that of surfactants thus they do
adsorb onto interfaces and self-assemble to form
micelles in solutions.
Figure 3 Types of homopolymer and copolymer
A number of triblock PEO-PPO-PEO copolymers
have been commercially available since 1950’s under
the generic name Poloxamers and the trademarks
Pluronic® (BASF, Mount Olive, NJ, USA) and
Synperonic® (ICI, Cleveland, UK) [1-5]. The
possibilities of large variation in total molecular
weight and block composition have led to a large
number of products.
The molecular weights of the commercially available
copolymers are typically in the 2000-20000 Da range
and their PEO contents in the 10-80% ranges.
II.
TYPES OF COPOLYMERS
Polymer may be homopolymer or copolymer
depending upon the type of monomer unit attached to
form long chain of polymer. Copolymers classify
according to shape and building architecture as well
as arrangement of monomeric group in polymer chain.
Basically copolymer can be classify either by
alternating, random, graft and block copolymer
(Figure 3). Further block copolymer may sub classify
as di-block or tri-block or multi-block copolymer
(Figure 4).
Figure 4 Types of block copolymer
The triblock architecture is the result of the
polymerization process where first a PPO
homopolymer is synthesized (constituting the
middle block of the copolymer) by the addition of
propylene oxide to the hydroxyl groups of
propylene oxide to the hydroxyl groups of
propylene glycol, and then ethylene oxide is added
at both ends of the PPO block to form the PEO endblocks. Figure 5 represents the formation of
micelles from different polymers.
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International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470
Figure 5 represents the formation of micelles from different polymers
III.
STIMULI
RESPONSIVE
COPOLYMERS
BLOCK
Stimuli
Responsive
polymers
have
some
environmental responding properties so that they can
swell or shrink corresponding to a small variation of
temperature, pH, and ionic strength. Their potential
applications in drug delivery, separation, and
bioswitch have been widely suggested. [7 - 9] Poly
(N-isopropylacrylamide) (PNIPAM) is a typical
example of such “smart” polymers, which can
undergo the coil-to-globule transition in water at its
low critical solution temperature (LCST ~32 °C) [10 –
12]. Micelles and aggregates from PS–PEO diblock
copolymers have been investigated by a number of
techniques for their potential use for encapsulation of
hydrophobic materials in an aqueous suspension.
Various morphologies, spheres, rods, lamellae, and
vesicles, in dilute aqueous solutions depending on the
molecular characteristics of PS–PEO diblock
copolymers have been reported. [13 – 16].
IV.
Figure 6 Self –assembly of amphiphilic block
copolymers
A Pluronic grid (Figure 7) was developed to provide
graphic representation of the relationship between
copolymer structure, physical form, and surfactant
characteristics [17].
SOLUTION
PROPERTIES
OF
AMPHIPHILIC BLOCK COPOLYMER
SURFACTANTS SYSTEMS
Formation of polymeric micelles from singlr block
copolymer is shown in below Figure 6.
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International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470
the surfactants performance in different industrial
formulations, Thus there has been a growing interest
both in basic and applied research. Likewise,
interaction of Pluronic® with sodium dodecyl
sulphate (SDS) using several techniques has also been
studied [35 – 38].
V.
Figure 7 Pluronic Grid
Temperature plays an important role on the
aggregation behavior. The presence of micellar
aggregates in solution gives rise to a certain value of
intermicellar potential. At certain value of
temperature, this potential reaches a very high value.
At initial temperature, the micellar aggregates are
hydrated by the water molecules, which is responsible
for screening the van der Waals forces between the
species. The increase in the temperature results in
dehydration of the copolymers blocks. As a result, the
van der Waals force (attractive potential between the
species) increases. At certain value of temperature,
this attractive force reaches a very high value to
impart phase separation. The performance based
properties of these polymeric surfactants can be
enhanced in presence of salts, hydrotropes and
organic additives such as alcohols, amines etc.
Recent studies on aqueous solution behaviour of
PEO–PPO– PEO block copolymers involve
micellization and phase behaviour and several
techniques have been employed to investigate the
self-assemblies formed. These include static and
dynamic light scattering [18-19], SANS [20 – 21],
static and time resolved fluorescence [22-24], FTIR
[25- 26], microcalorimetry [27], cryo- TEM [28],
surface tension [29 - 30], viscosity [18, 31],
oscillatory shear measurements [18, 32], and sound
velocity/ultrasonic absorption method [33 - 34] etc.
The aggregation and aggregate structures have been
examined at different temperatures and in the
presence of additives like inorganic salts,
nonelectrolytes, hydrotropes and ionic surfactants.
Micellar solutions of mixed surfactants exhibit
remarkably different behavior from those of single
surfactants and this property can be used to optimize
APPLICATIONS
The wide variety of application of polymer-surfactant
mixed systems in aqueous solutions has thus
motivated both chemists and biologists. Block
copolymers have low toxicity and due to their
nontoxic properties and surface-activity they have
found application in the areas of biomaterials, protein
separation, drug delivery and cardiovascular
therapeutics and as industrially important surfactants.
Amphiphilic poly(ethylene oxide)–poly(propylene
oxide) block copolymers are thermoresponsive
materials that display unique aggregation properties in
aqueous medium. In solutions at concentration above
a critical concentration (CMC) surfactant molecules
tend to aggregate and form micelles. In the presence
of large polymers, surfactant micelles can form selfassembled complexes. These complexes play a
fundamental role in a broad range of industrial
applications, including colloid stabilization and
detergency, and are increasingly found in commercial
surfactant
formulations
such
as
foods,
pharmaceuticals, cosmetics, textiles, polymers, paints,
and paper [39- 42]. Over the years, therefore, micelles
have been of interest to pharmacological scientists
either as drug delivery systems or as targeting
systems. Amphiphilic drugs solubilize in body fluids
and interact with membranes in the organism before
they reach their final targets. Aggregates of these
amphiphilic drugs could act as their own carriers.
Future Challenges needs suitable, effective drug
delivery or targeting systems.
VI.
CONCLUSIONS
Over the past two decades, new surfactant molecules
have been appearing at a relatively rapid pace.
Scientific curiosity has also driven surfactant science
research to focus on surfactant molecules having
interesting fabricated shapes and structures.
Fundamental knowledge of surfactant is very essential
although surfactant science is now very well
established discipline and there is still room for new
molecules designed for specific purposes and new
applications.
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International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470
ACKNOWLEDGEMENT
Dr. Tejas P Joshi would like to thank Prof. N. C.
Desai, Head, Dept. of Chemistry, Maharaja
Krishnakumarsinhji
Bhavnagar
University,
Bhavnagar, for honest support.
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